1. Field of the Invention
This invention relates to sequential biological/chemical/biological treatment providing improved remediation of undesired organic solid components in materials such as soils, sediments, sludges and slurries containing such solid organopollutants, particularly polynuclear aromatic hydrocarbons (PAH's) and polychlorinated hydrocarbons (PCBs). The process generally involves biological treatment of contaminated solid materials under aerobic conditions followed by chemical oxidation or partial oxidation with hydrogen peroxide in the presence of ferrous ion, such as Fenton's Reagent (H.sub.2 O.sub.2 /Fe.sup.++), under specified conditions followed by aerobic microbial digestion.
2. Description of Prior Art
A number of prior art references teach treatment of organic-containing effluents with hydrogen peroxide and iron. U.S. Pat. No. 4,321,143 teaches decreasing COD-content of effluent by treating with hydrogen peroxide in the presence of a transition metal compound, for decomposition of the hydrogen peroxide, by adjusting the pH of the effluent to about 4 to 5, adding about 55 to 63% of the calculated quantity of H.sub.2 O.sub.2 required for the total oxidation of the total COD-content, dissolving an iron compound in the effluent so that the molar ratio of H.sub.2 O.sub.2 to iron is about 20:1 to 10:1, maintaining the temperature at about 5.degree. to about 100.degree. C., adding a base to adjust the pH to about neutral, separating flocculated material, and subjecting the effluent to biological degradation.
Oxidation of certain aromatic chemicals using Fenton's Reagent is known: U.S. Pat. No. 4,604,214 teaches removal of nitrocresols from dinitrotoluene waste water streams by adjustment of pH to below about 4 with an aqueous acid followed by contact with Fenton's Reagent, about 1.1 to 3.0 weight ratio of peroxide to total nitrocresols and ferrous salt to provide 2.5-5.times.10.sup.-3 M, at 70.degree. to 90.degree. C. for about one half to one hour; U.S. Pat. No. 4,804,480 teaches destroying polynitrophenols or their salts in an aqueous waste by treating with at least two moles of hydrogen peroxide per mole of nitrophenol in the presence of from 0.002 to 0.7 moles of an iron salt per mole of polynitrophenol and at a pH lower than 4 and a temperature greater than 65.degree. C.; U.S. Pat. No. 4,370,241 teaches treatment of waste water containing phenol or a phenol derivative with hydrogen peroxide in the presence of metallic iron or copper with a specified activator which is a salt of an alkali metal, alkaline earth metal, zinc, aluminum, nickel, manganese or insoluble silica, the activator being present in an amount of 0.1 to 0.2 percent based upon the hydrogen peroxide, and the treatment is said to be independent of pH.
U.S. Pat. No. 4,724,084 teaches removal of toxic organics and heavy metals from waste water discharged from airplane manufacturing processes by using ferrous sulfate catalyzed hydrogen peroxide at an initial pH of about 5 for oxidation of phenol followed by flocculation of metals and repeating the oxidation step with ferrous sulfate catalyzed hydrogen peroxide.
Soil decontamination by desorption and dehalogenation of polyhalogenated contaminants is taught by U.S. Pat. No. 4,447,541 to be effected by an alkaline constituent of an alkali metal hydroxide and a monohydric or dihydric alcohol together with a sulfoxide catalyst followed by biological degradation of the more highly biodegradable hydrolyzed organics. U.S. Pat. No. 4,387,018 teaches removal of polychlorinated biphenyl from oil by extracting the biphenyls into methanol and separation by distillation.
The publication "Biodegradation of Old Town Gas Site Wastes," Vipul J. Srivastava, John J. Kilbane, Robert L. Kelley, Cavit Akin, Thomas D. Hayes and David G. Linz, IGT Symposium on Gas, Oil, and Coal Biotechnology, New Orleans, La., Dec. 5-7, 1988 generally suggests treatment of pyrene and thianthrene with hydrogen peroxide and ferrous sulfate for oxidizing polynuclear aromatic hydrocarbons to complement in-situ biological treatment processes.
A recent review of bioremediation of liquid and solid organic contaminated wastes which points out many problems, particularly in the bioremediation of solids contaminated with aromatic hydrocarbons, most particularly the polynuclear aromatic hydrocarbon contaminants having about 4 to about 6 rings, is provided in "Bioremediation of Gas Industry Wastes: Current Status and New Directions," W. Kennedy Gauger and Vipul J. Srivastava, Hazardous Waste and Environmental Management in the Gas Industry Symposium, Chicago, Ill. Jun. 13, 1990.